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View Full Version : TDR, fault finding, test pictures


1idejim
10-28-2010, 08:53 PM
i have a few pictures of TDR tests, how to find the faulted wire and the method of locating a fault without first locating the wire path.

first set is how i determine which wire in a pair is faulted.

1. with the dmm set to 2000k ohms insert the black probe directly into the ground (you may have to wet the ground in the summer, don't make mud) and zero out the dmm and de-energize the wire path (just touch both wires together.

2. touch the red probe to each wire separately, the non-compromised wire should read ol, the faulted wire will have some readable resistance and depending upon the severity of the fault and the conductivity of the soil could actually read continuity.

it's that simple

1idejim
10-28-2010, 10:13 PM
1. reading of 29'0 short

2. calibration of V.O.P. 55%

3. actual measurement

4. this was more of a test i had been wanting to do to find out what the TDR would do with 2 totally different wires, it actually read the accurate one way distance to a short, unusual do to the testing and work we have been doing with irrigation has been a looped reading on a zone valve which would have been twice the distance.

i have been using the TDR for almost 10 years and i am learning something every time i use it.

btw the actual length of the wire is 30'

Pro-Scapes
10-28-2010, 10:18 PM
I have always taken this for granted. I was taught this many years ago but I am in the practice that if a cable is comprimised it usually needs to be replaced becuause I cannot vouch for the performance of that cable once its been damaged.

There are of course exceptions to this

Prolightscaper
10-28-2010, 10:32 PM
I have always taken this for granted. I was taught this many years ago but I am in the practice that if a cable is comprimised it usually needs to be replaced becuause I cannot vouch for the performance of that cable once its been damaged.

There are of course exceptions to this

With the cost of cable now it may be prudent to repair in lieu of replace whenever possible and viable.

bcg
10-28-2010, 11:05 PM
Obviously, you also need to consider the wire path. A 30' straight run in turf, no question, just replace it. A 150' run that passes under hardscape or some other difficult obstacle, I'm going to make a real effort to repair first.

David Gretzmier
10-29-2010, 12:41 AM
once you find the break, I cut back til I see all pure clean copper. then I replace. often times, you never find good clean copper. it may get cleaner, but I keep cutting til all black is gone. it never ceases to amaze me how far copper corrosion can go inside wire insulation, literally hundreds of feet.

INTEGRA Bespoke Lighting
10-29-2010, 06:48 AM
I am not sure that using these tools and techniques to find a 'ground fault' is all that efficient. Time is money right?

Yesterday I was called out to a job where the "lights are not coming on". Spent 10 mins diagnosing the situation. Found that the maintenance guy had just aerated the "lawns". (Soils are very shallow here and filled with tree roots) One of the LV circuit wires that fed the relay between Zone 1 and Zone 2 had obviously been cut or damaged. Sure enough none of the 3 fixtures on that circuit were alive and the rest were. Pulled the wire out of the ground, found the break, cut back to clean copper, spliced, and slit trenched the wire back in the ground. Time on the repair? 10 minutes. Total time on site = 20 Mins. Materials used = 2' of 12/2 and 4 connectors.

How long would I have spent there had I gone searching with different meters, then analyzing the readings, then uncovering the wire hopefully where the meter told me the fault was, etc? (not to mention the cost of the meters that would have to be amortized into the cost of the service call) Sometimes the 'brute force' method is the most efficient and most cost effective. Even if I had opted to replace the entire 50 or 60 feet of 12/2 it would only have cost a few bucks.

I do have a cable locater, and it comes in handy once or twice a year. (Generally when a circuit has been sheared off by excavator equipment and you cannot find the "other end"). But generally we just use a logical, stepwise system of diagnosis and then pull the wire out between point A and B.

Pro-Scapes
10-29-2010, 07:22 AM
We cut an irrigation wire on the project we are working on now. 8 strand. Distance to timer about 150 ft. Distance to valve box (3 valves inside and thats all this wire was feeding) about 40 ft. My brother was with me and he wanted to grab a foot of wire and splice it back up.

I said no and wanted to put a box in the ground near the conduit of the driveway and then splice it and replace the 40 ft to the valve. He tried it his way and there was at least 2 more cuts between the first one and the valves. My reasoning was Splice is in a box and we care confident the cable is intact. I would hate to be called back a couple mo later because he thinks we messed up his irrigation and I am getting erratic or intermittant problems with his wiring.

His time spent messing with it trying to find problems was 2 hours. My time spent replacing it after I took over... 30-40 min plus now I know the area we were in is intact.

James, with your areated lawn. How can you be sure there are not nicks or other comprimises in your cable. Areation damage is automatic replacement at LEAST across the area it was done in. . I dont care if i will be in and out in 20 min or 4 hours.

INTEGRA Bespoke Lighting
10-29-2010, 07:36 AM
Billy. I pulled the entire 50 - 60' of wire out of the ground. It was only hit in one place.

Pro-Scapes
10-29-2010, 08:03 AM
Billy. I pulled the entire 50 - 60' of wire out of the ground. It was only hit in one place.

You...arrived on site... located cut...pulled 50 to 60 ft of wire up. Repaired and reburied in 20 min ?:confused:

1idejim
10-29-2010, 08:22 AM
I am not sure that using these tools and techniques to find a 'ground fault' is all that efficient. Time is money right?

Yesterday I was called out to a job where the "lights are not coming on". Spent 10 mins diagnosing the situation. Found that the maintenance guy had just aerated the "lawns". (Soils are very shallow here and filled with tree roots) One of the LV circuit wires that fed the relay between Zone 1 and Zone 2 had obviously been cut or damaged. Sure enough none of the 3 fixtures on that circuit were alive and the rest were. Pulled the wire out of the ground, found the break, cut back to clean copper, spliced, and slit trenched the wire back in the ground. Time on the repair? 10 minutes. Total time on site = 20 Mins. Materials used = 2' of 12/2 and 4 connectors.

How long would I have spent there had I gone searching with different meters, then analyzing the readings, then uncovering the wire hopefully where the meter told me the fault was, etc? (not to mention the cost of the meters that would have to be amortized into the cost of the service call) Sometimes the 'brute force' method is the most efficient and most cost effective. Even if I had opted to replace the entire 50 or 60 feet of 12/2 it would only have cost a few bucks.

I do have a cable locater, and it comes in handy once or twice a year. (Generally when a circuit has been sheared off by excavator equipment and you cannot find the "other end"). But generally we just use a logical, stepwise system of diagnosis and then pull the wire out between point A and B.

it seems to me that the general consensus is that i am wasting both of our time, i was just trying to be helpful and share some experience.

i can understand that learning to use a locator or fault finder would be a waste of time if your time if your preferred method of diagnosis and repair is the "grip it and rip it" method.

if you dealt with difficult ground and a minimum cover requirement for LV was enforced this would not be your first course of action.

i was under the impression that there was more craftsmanship and professionalism involved in the LVL industry, now i realize that even though many of you cast aspersions at landscapers, handymen, hacks and home owners for their methods, applications and intrusion of the LVL industry you seem to diagnose and troubleshoot at a level near theirs, i hope you don't speak for the majority.

i'll stick to the irrigation forum where a certain amount of skill and finesse is required to diagnose a wiring issue not just a good set of forearms.

i thank you for both your time and input. :waving:

Mark B
10-29-2010, 08:40 AM
See what I mean?
Posted via Mobile Device

Kiril
10-29-2010, 08:42 AM
if you dealt with difficult ground and a minimum cover requirement for LV was enforced this would not be your first course of action.

Anyone who shallow buries wire of any kind in turf gets what they deserve when it gets damaged due to standard turf maintenance practices, and should be fixing damage on their dime until the wire is properly buried.

INTEGRA Bespoke Lighting
10-29-2010, 08:56 AM
it seems to me that the general consensus is that i am wasting both of our time, i was just trying to be helpful and share some experience.

i can understand that learning to use a locator or fault finder would be a waste of time if your time if your preferred method of diagnosis and repair is the "grip it and rip it" method.

if you dealt with difficult ground and a minimum cover requirement for LV was enforced this would not be your first course of action.

i was under the impression that there was more craftsmanship and professionalism involved in the LVL industry, now i realize that even though many of you cast aspersions at landscapers, handymen, hacks and home owners for their methods, applications and intrusion of the LVL industry you seem to diagnose and troubleshoot at a level near theirs, i hope you don't speak for the majority.

i'll stick to the irrigation forum where a certain amount of skill and finesse is required to diagnose a wiring issue not just a good set of forearms.

i thank you for both your time and input. :waving:

I did not mean any offense by my post. I just wanted to illustrate that there are other ways to diagnose and repair faults. It is good that there are tools out there to help us and your products and instructions are certainly valid and helpful. Different situations call for different approaches.

As for the installation of the LV wire on this property... I assure you it was done to the best of anyone's ability. Please don't be so quick to judge a situation that you don't fully understand. Installation of any and all infrastructure in our market is challenging to say the least. Shallow to no soil cover, exposed or barely covered rock, and roots everywhere. It is something we have to deal with on most properties here. I can certainly see how tools such as yours would come in very handy and helpful in most typical urban/suburban markets, where pulling up the wire would be invasive and time consuming.

Please continue to support and contribute here. :)

1idejim
10-29-2010, 09:53 AM
I did not mean any offense by my post. I just wanted to illustrate that there are other ways to diagnose and repair faults. It is good that there are tools out there to help us and your products and instructions are certainly valid and helpful. Different situations call for different approaches.

As for the installation of the LV wire on this property... I assure you it was done to the best of anyone's ability. Please don't be so quick to judge a situation that you don't fully understand. Installation of any and all infrastructure in our market is challenging to say the least. Shallow to no soil cover, exposed or barely covered rock, and roots everywhere. It is something we have to deal with on most properties here. I can certainly see how tools such as yours would come in very handy and helpful in most typical urban/suburban markets, where pulling up the wire would be invasive and time consuming.

Please continue to support and contribute here. :)

i was not offended, i'm used to resistance.

irrig8r
10-29-2010, 11:24 AM
Jim,
I'll assume that James was working on a job he installed and therefore knew the layout already. Otherwise he wouldn't have been able to get to it that quickly.

Am I right James? How would you approach troubleshooting a job you've never seen before?

BTW James, ever consider conduit when going through lawns or flower beds where chances of damage are higher? How deep do you go in a lawn?

And Jim, my understanding of standard LVL practice is no deeper than 6"... sometimes I've run across it just covered with mulch.

cheese189
10-29-2010, 11:33 AM
How did you determine the VOP at 55%? Manufacturers rating or calibrating to a known length? Because with 2 different wires, it should be a problem. Were the wires tested twisted together or otherwise related to each other or direct buried in the same trench but not physically maintaining a consistent relationship on the run? Also, on your previous post you set the DMM at 2000K range. Any experienced issues with ranges over 2000K? Very interesting stuff for us nerds.

1idejim
10-29-2010, 02:19 PM
i live in the country and use a mercury drive for internet connection, uploading is terrible the last 2 days, pardon me.

Jim,
I'll assume that James was working on a job he installed and therefore knew the layout already. Otherwise he wouldn't have been able to get to it that quickly.

Am I right James? How would you approach troubleshooting a job you've never seen before?

BTW James, ever consider conduit when going through lawns or flower beds where chances of damage are higher? How deep do you go in a lawn?

And Jim, my understanding of standard LVL practice is no deeper than 6"... sometimes I've run across it just covered with mulch.

gregg, here is a link for viewing www.cast-lighting.com/learning/articles/4_article_Wire

here is a quick copy taken from the link:
National Electric Code (NEC) Requirements for Burial of Low Voltage Wiring

According to article 300.5 of the 2005 NEC Code, low voltage landscape lighting wire needs to be buried to the following depths:
Location of Wire

Minimum Burial Depth*
All locations not specified below
6 inches
In trench below minimum 2" thick concrete
6 inches
Under a building
In raceway only
Under roads, alleys, public driveways and parking lots
24 inches
Under one- and two-family dwelling driveways and outdoor parking areas and used only for dwelling-related purposes
18 inches
In or under airport runways, including adjacent areas where trespassing is prohibited
18 inches
*Note – depth is measured from the top surface of wire to top surface of finished grade or surface material. Where solid rock prevents compliance with these depths, a direct burial raceway can be used, encased in concrete at least 2" thick on top and extending down to the rock.
(Document No. 00054: Created on: 07/12/08 Last modified on: 08/26/09)

i don't doubt that james would be able to cold call a system, have three lights in a row not working and safely assume that the compromise followed the last working fixture, this is the same reasoning which we would use to assume a common wire issue if a series of valves quit working.

How did you determine the VOP at 55%? Manufacturers rating or calibrating to a known length? Because with 2 different wires, it should be a problem. Were the wires tested twisted together or otherwise related to each other or direct buried in the same trench but not physically maintaining a consistent relationship on the run? Also, on your previous post you set the DMM at 2000K range. Any experienced issues with ranges over 2000K? Very interesting stuff for us nerds.

that TDR has a library of something like 30 factory presets and free range of 99 percentage increments, i calibrate with some set measured pairs in different gauges.
i've been working with the TDR for almost 10 years (i can't really remember when i bought my first) and have been testing it since.

i was shown how to test for earth to ground resistance by an electrician at a water treatment plant in 1979, never used it until i started with irrigation troubleshooting.

with an analog meter you set the scale @1,000k. 2,000 is what the average adjustable dmm uses. something like 200, 2000, 20k, 200k, 2000k.

an irrigation wire above 700,000 usually indicates a good wire path, below suggests that you have a nick or break. with irrigation this is more relevant than with LVL. i just mentioned it because you can tell right away if you have earth contact or not, being able to determine the compromised wire is a byproduct of this resistance test.

i am far from an expert electrician and any of you know more about LVL than i do but i can troubleshoot, test, analyze, diagnose and locate with some pretty good hands, the reason is i have lots of tools, i constantly research my craft and when i am not working on a job, i am running problems around in my head and working them out in practice.

another thing that i do is keep a log of locates, troubleshooting jobs and installs. i can look back if i get a head scratcher and usually have the solution either as a past experience or as an idea for a test that i want to run.

Tim R.
11-06-2010, 08:35 AM
This is good stuff. Thanks for sharing Jim. I have always used a combination of Pulser fault locators for locating direct ground faults in cable and wire locators for tracking the run of wire and fault locations. I have never used a TDR meter, but I can see it's relevance if you know the track of the wiring. This shows me I need to study the technical side of fault location a bit more. I have followed you over on the irrigation site and you always have good input over there. Thanks for contributing here.

1idejim
11-07-2010, 03:44 PM
This is good stuff. Thanks for sharing Jim. I have always used a combination of Pulser fault locators for locating direct ground faults in cable and wire locators for tracking the run of wire and fault locations. I have never used a TDR meter, but I can see it's relevance if you know the track of the wiring. This shows me I need to study the technical side of fault location a bit more. I have followed you over on the irrigation site and you always have good input over there. Thanks for contributing here.

thanks tim.

if you ever decide to buy a TDR let me know and i'll recommend a few (they aren't the same) and i'll send you a copy of some methods that i have found to be successful

Pro-Scapes
11-07-2010, 06:02 PM
this is a great thread but i am banking it is over alot of guys heads. I always start a troubleshooting call by first stepping back and taking a good look around and stopping to think. Often the complex issues have a very logical explaination or simple problem.

1idejim
11-07-2010, 06:48 PM
this is a great thread but i am banking it is over alot of guys heads. I always start a troubleshooting call by first stepping back and taking a good look around and stopping to think. Often the complex issues have a very logical explaination or simple problem.

what approach do you use when you encounter a complex issue with no logical explaination from your viewpoint? that is the question i ask myself daily, i try to prepare for the nightmares and the others are just a bunch of bad dreams.

Pro-Scapes
11-07-2010, 07:15 PM
what approach do you use when you encounter a complex issue with no logical explaination from your viewpoint? that is the question i ask myself daily, i try to prepare for the nightmares and the others are just a bunch of bad dreams.

Isolation.Start at the head of it and work your way down. Before I will assume its a bad wire or fault I will check connections... sockets...do my wiggle test etc. If it comes to a point I cant readily isolate a problem with a given run on someone elses system there is 95% of the time multiple issues with either quality or workmanship anyways where I will either offer to leave the system alone or repair it correctly. I am not going to waste my time and the customers money on a system thats a failure from the start.

I rewire alot of fair quality systems that were just installed wrong to begin with. I know irrigation is somewhat different in that you do not have to worry about v drop but im sure you have found your share of problems that were just plain crap workmanship.

I also realize the clientel can often be different but I find my clients would rather just have it done right. Im not willing to put my name on repairing a joke of a system only for them to have to call me back 3 mo later because they have issues with another part.

No logical explaination ? Do a search for my thread called "the unexplained" Maybe you can figure it out

Kiril
11-07-2010, 08:22 PM
I know irrigation is somewhat different in that you do not have to worry about v drop

Certainly you jest .... right?

The Lighting Geek
11-07-2010, 09:11 PM
what approach do you use when you encounter a complex issue with no logical explaination from your viewpoint? that is the question i ask myself daily, i try to prepare for the nightmares and the others are just a bunch of bad dreams.

I have never found a problem in 25+ years that did not have an answer. Billy nailed it when he said you need step and use your noggin first. Many times the problem is someone else doing bad work. So after many years of finding unbelievable crap, I first try to think like they would...LOL! Honestly, we all have had our share of the dumbest, most illogical stuff mixed with the logical.

I did a LOT of irrigation repair, wire tracking, finding valves, nick in wire, etc. It helped me a great deal in lighting repair.

1idejim
11-12-2010, 09:46 PM
Isolation.Start at the head of it and work your way down. Before I will assume its a bad wire or fault I will check connections... sockets...do my wiggle test etc. If it comes to a point I cant readily isolate a problem with a given run on someone elses system there is 95% of the time multiple issues with either quality or workmanship anyways where I will either offer to leave the system alone or repair it correctly. I am not going to waste my time and the customers money on a system thats a failure from the start.

I rewire alot of fair quality systems that were just installed wrong to begin with. I know irrigation is somewhat different in that you do not have to worry about v drop but im sure you have found your share of problems that were just plain crap workmanship.

I also realize the clientele can often be different but I find my clients would rather just have it done right. Im not willing to put my name on repairing a joke of a system only for them to have to call me back 3 mo later because they have issues with another part.

No logical explanation ? Do a search for my thread called "the unexplained" Maybe you can figure it out

http://www.lawnsite.com/showpost.php?p=2647094&postcount=1

below are a couple things that i would consider in the "unexplained" scenario billy. one of my best friends is a lineman, we discuss all forms of power on a regular basis and its amazing of the parallels

http://en.wikipedia.org/wiki/Stray_voltage#Coupled_and_induced_voltages

http://www.coleparmer.com/techinfo/techinfo.asp?htmlfile=Fluke-volt-affects.htm&id=292

i am not here to knock your methods billy, just tried to introduce a few new, but proven methods of troubleshooting, your reluctance is noted.